Biomass Production in Ornamental Foliage Plants: Crop Productivity and Mechanisms Associated with Exogenous Cytokinin

DI BENEDETTO, A; TOGNETTI, J.; GALMARINI, C.R

The Americas Journal of Plant Science and Biotechnology

Global Science Books

Año: 2010 p. 1 - 22

1752-3877

An important mediator of shoot physiological processes associated to the biomass production can be the supply of signal molecules (other than water and nutrients) from the root system. Root-to-shoot signaling is often considered to be important in regulating shoot growth when soil conditions determine a change in shoot water or nutrient status. There are strong indications that cytokinins are root factors which are transported via the xylem to the shoot where they exert a major regulatory influence on growth and photosynthesis. Cytokinins play a critical role in many aspects of plant growth and development, including the regulation of the apical dominance, root growth and plastid differentiation. Although it has long been known that the cytokinin signal transduction pathway actively interacts with other pathways, particularly with light and auxin pathways, details of these interactions remain poor understood. My results showed that exogenous BAP spray solutions increased both fresh weight and dry weight for the E. aureum, F. benjamina ‘green’ and ‘variegated’ ornamental plants tested through higher relative growth rate (RGR), leaf expansion rate (LER), net assimilation rate (NAR) and leaf area ratio (LAR). These responses are supported by a higher photosynthetic activity and a fast leaf area expansion as a result of a decrease in the leaf plastochron, an increase in leaf expansion through changes in both leaf thickness and intercellular spaces extension. The increase of photosynthate partitioning behalf the shoot apical meristem has been associated to a positive feed-back during the first 30 days after the exogenous BAP spray. An interaction between BAP and the photosynthetic light integral has been found. The inductive nature of the hormonal stimuli and a lack of BAP:AIA interaction on the foliage plants response has been identified. Finally, the well documented thigmomorphogenetic response in E. aureum has been associated with the cytokinin translocation from plants cultivated on floor, climbed or downward. The technological use of this information on cultivation of ornamental shade plants is still unclear because knowledge about cause-effect relationships between exogenous cytokinin supply and plant response is still scarce. Regulatory processes conditioned the balanced growth of roots and shoots and the conclusion that root cytokinins are part of the signaling pathway can be drawn.